JP2024055292A - Laminated Film - Google Patents

Abstract

To provide a laminated film that reduces the likelihood of the occurrence of breakage and color loss due to molding, can be suitably used for molding under a condition where a high temperature load is applied thereto, and is suitable for metallic decoration.SOLUTION: A laminated film has three or more different types of thermoplastic resin layers, has three or more continuous regular arrays formed by the three or more types of thermoplastic resin layers, has an average reflectance at wavelengths from 400 nm to 800 nm of 35% or more and 100% or less, and when the film is drawn by 30% at 100°C in a main orientation axis direction and a main orientation axis orthogonal direction, has an average reflectivity change ΔR1 at wavelengths from 400 nm to 800 nm of 0.1% or more and 20% or less.SELECTED DRAWING: None

Description

The present invention relates to a laminated film that is resistant to tearing and discoloration during molding, can be used effectively for molding under high-temperature load conditions, and is suitable for metallic decoration.

Light control films capable of blocking and extracting light rays in a specific wavelength band have been put to practical use in a wide range of fields for the purpose of preventing deterioration of the internal environment and components of products from environmental factors such as light and heat rays, and for the purpose of extracting only light rays in a specific wavelength band to produce a desired color tone. Representative examples include infrared-cutting films for building materials and automobiles to suppress indoor temperature increases, and ultraviolet-cutting films for industrial materials to absorb excess ultraviolet rays during ultraviolet laser surface processing. In the electronic device field, blue-light-cutting films that block blue light emitted from display light sources that is harmful to the eyes, and brightness-enhancing films that can retroreflect diffused and lost backlight light are used, and metallic-toned films that reflect the entire visible light range to give a metallic look are used for automobile interior materials and mobile housing applications.

Conventionally, metallic films have been known in which a thin metal layer is applied to one side of a resin film by methods such as vapor deposition or sputtering, and are used primarily for decorative purposes. However, such metallic films can lack formability and have problems such as the metal layer easily peeling off or cracking during molding.

As a metallic film that addresses these problems, laminated films that utilize interference reflection have been proposed. For example, laminated films have been proposed that have an (AB)m structure (m is a natural number representing the number of repeating units) in which two layers with different refractive indices (layer A, layer B) are alternately laminated (e.g., Patent Documents 1 to 3), and laminated films have an (ABC)m structure (m is a natural number representing the number of repeating units) in which three layers with different refractive indices (layer A, layer B, layer C) are regularly laminated to obtain a film with a wider range of reflectance (e.g., Patent Document 4).

JP 8-503312 A JP 2018-001488 A JP 2010-184493 A Japanese Patent Application Laid-Open No. 4-313704

In laminate films of the type in which two types of thermoplastic resins with different refractive indices are regularly laminated to reflect light in the visible light range to obtain a metallic tone, such as the laminate films of (AB)m structure (m is a natural number representing the number of repeating units) disclosed in Patent Documents 1 to 3, the difference in refractive index between the two thermoplastic resins is small because there are two types of thermoplastic resin, and when the laminate film is thinned by molding, the reflectance decreases and it may not be possible to maintain the metallic tone. Furthermore, in such laminate films, if a resin with a large refractive index difference is used to maintain the metallic tone even after molding, color loss and tearing due to delamination may occur, making molding difficult.

The laminated film with an (ABC)m structure (m is a natural number representing the number of repeating units) disclosed in Patent Document 4 is intended to be used mainly as an infrared cut film, and has poor formability. As a result, it is sometimes difficult to perform the desired molding process due to the inability to mold uniformly, resulting in uneven coloring, and delamination during molding.

The present invention aims to eliminate the above-mentioned shortcomings, provide a laminated film that is resistant to tearing and discoloration during molding, can be suitably used for molding under conditions of high temperature load, and is suitable for metallic decoration.

In order to solve the above problems, the present invention has the following configuration.
(1) A laminated film having three or more different thermoplastic resin layers, having three or more consecutive regular arrays formed by the three or more types of thermoplastic resin layers, having an average reflectance of 35% or more and 100% or less at wavelengths of 400 nm to 800 nm, and having an average reflectance change ΔR1 of 0.1% or more and 20% or less at wavelengths of 400 nm to 800 nm when stretched 30% at 100° C. in the main orientation axis direction and in the direction perpendicular to the main orientation axis.
(2) A laminated film having three or more different thermoplastic resin layers, having three or more consecutive regular arrays formed by the three or more types of thermoplastic resin layers, having a chroma C* of 0.1 to 20, and having a chroma change ΔC* of 0.1 to 15% when stretched 30% at 100° C. in the main orientation axis direction and in the direction perpendicular to the main orientation axis.

The laminate film of the embodiment (1) below and the laminate film of the embodiment (2) below are sometimes referred to as the first laminate film of the present invention and the second laminate film of the present invention, respectively. In addition, both are sometimes collectively referred to as the laminate film of the present invention.

The laminated film of the present invention can also be in the following form, and can also be made into a decorative film or a molded article as described below.
[1] A laminated film having three or more different thermoplastic resin layers, having three or more consecutive regular arrays formed by the three or more types of thermoplastic resin layers, having an average reflectance of 35% or more and 100% or less at a wavelength of 400 nm to 800 nm, and having an average reflectance change ΔR1 of 0.1% or more and 20% or less at a wavelength of 400 nm to 800 nm when stretched by 30% at 100° C. in the main orientation axis direction and in the direction perpendicular to the main orientation axis.
[2] A laminated film having three or more different thermoplastic resin layers, having three or more consecutive regular arrangements formed by the three or more types of thermoplastic resin layers, having a chroma C* of 0.1 to 20, and having a chroma change ΔC* of 0.1 to 15% when stretched 30% at 100° C. in the main orientation axis direction and in the direction perpendicular to the main orientation axis.
[3] The laminate film according to [1] or [2], characterized in that the peeling rate of the squares in an adhesion test based on the cross-cut method specified in JIS K 5600-5-6:1999 is 10% or less.
[4] The laminate film according to any one of [1] to [3], wherein at least one of the three or more different thermoplastic resin layers is a thermoplastic resin layer exhibiting crystallinity.
[5] The laminate film according to [4], wherein at least one of the thermoplastic resin layers exhibiting crystallinity is composed mainly of polyethylene terephthalate or polyethylene naphthalate.
[6] The laminate film according to any one of [1] to [5], wherein the thermoplastic resin layers constituting the regular arrangement are of three types.
[7] The laminate film according to [6], wherein the three types of thermoplastic resin layers constituting the regular arrangement are a combination of crystalline/amorphous/amorphous thermoplastic resin layers.
[8] The laminate film according to [7], wherein at least one of the amorphous thermoplastic resin layers is mainly composed of any one of acrylic, polyester having an alicyclic structure, polyolefin, and polyamide.
[9] The laminate film according to any one of [1] to [8], characterized in that the average reflectance at wavelengths of 400 nm to 800 nm is 35% or more and 100% or less, and when stretched by 50% at 100° C. in the main orientation axis direction and in the direction perpendicular to the main orientation axis, the average reflectance change ΔR2 at wavelengths of 400 nm to 800 nm is 0.1% or more and 20% or less.
[10] The laminate film according to any one of [1] to [9], characterized in that (λ·R)/t is 820 or more and 1400 or less, where λ [nm] is the reflection bandwidth of the widest reflection band Π in which the reflectance is continuously 20% or more over 100 nm or more in the wavelength range of 300 to 2600 nm, R [%] is the average reflectance in the reflection band, and t [μm] is the film thickness.
[11] The laminate film according to any one of [1] or [3] to [10], characterized in that the chroma C* is 0.1 to 20, and the chroma change ΔC* when stretched 30% in the main orientation axis direction and in the direction perpendicular to the main orientation axis at 100° C. is 0.1% to 15%.
[12] A decorative film comprising the laminate film according to any one of [1] to [11].
[13] A molded body using the decorative film according to [12].

The present invention provides a laminated film that is resistant to tearing and discoloration during molding, can be used effectively for molding under high-temperature load conditions, and is suitable for metallic decoration.

FIG. 2 is a schematic diagram showing the wavelength band Π, the reflection bandwidth λ, and the average reflectance in the reflection spectrum of the laminate film according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the wavelength band Π, the reflection bandwidth λ, and the average reflectance in the reflection spectrum of a laminate film according to one embodiment of the present invention (an embodiment different from that of FIG. 1 ). FIG. 3 is a schematic diagram showing the wavelength band Π, the reflection bandwidth λ, and the average reflectance in the reflection spectrum of a laminate film according to one embodiment of the present invention (an embodiment different from the embodiments of FIGS. 1 and 2). FIG. 4 is a schematic diagram showing the wavelength band Π, the reflection bandwidth λ, and the average reflectance of the reflection spectrum of a laminate film according to one embodiment of the present invention (an embodiment different from the embodiments of FIGS. 1 to 3).

The laminated film of the present invention is described in detail below.

The first laminate film of the present invention is a laminate film that has three or more different types of thermoplastic resin layers, has three or more consecutive regular arrays formed by the three or more types of thermoplastic resin layers, has an average reflectance of 35% or more and 100% or less at wavelengths of 400 nm to 800 nm, and has an average reflectance change ΔR1 of 0.1% or more and 20% or less at wavelengths of 400 nm to 800 nm when stretched 30% at 100°C in the main orientation axis direction and in the direction perpendicular to the main orientation axis.

The second laminate film of the present invention is a laminate film characterized in that it has three or more different thermoplastic resin layers, has three or more consecutive regular arrangements formed by the three or more thermoplastic resin layers, has a chroma C* of 0.1 to 20, and has a chroma change ΔC* of 0.1 to 15% when stretched 30% at 100°C in the main orientation axis direction and in the direction perpendicular to the main orientation axis.

The laminated film of the present invention has three or more different thermoplastic resin layers. In the laminated film of the present invention, the thermoplastic resin layers are "different" if: (1) they have different compositions; (2) they have different glass transition temperatures or melting points in differential scanning calorimetry (DSC); or (3) the brightness of each layer is different in a dyed image when the cross section is observed with a transmission electron microscope (TEM).

"Different compositions" means that the conditions below for "same composition" are not met. "Same composition" means that the ordered arrangement of the chemical structure of the thermoplastic resins that make up each thermoplastic resin layer is 95 mol% or more in common, or that 95 mass% of the components are in common when comparing the components of each thermoplastic resin layer.

For example, in the case of the former, polyethylene terephthalate has as its main constituent unit a constituent unit (ethylene terephthalate unit) in which ethylene glycol units and terephthalic acid units are bonded by ester bonds, but when the resin constituting the layer has a common chemical structure of polyethylene terephthalate but the amount of copolymerization component exceeds 5 mol%, such as a layer of homopolyethylene terephthalate and a layer of polyethylene terephthalate copolymerized with 10 mol% isophthalic acid, the two are considered to have different compositions. In addition, in the case of the latter, when the same constituent component is the main component but 5% of the component is different, such as a layer consisting only of homopolyethylene terephthalate and a layer containing 90% homopolyethylene terephthalate by mass with the remaining 10% by mass being other components, the two are also considered to have different compositions.

The specific composition/regular arrangement structure of the chemical structure of each thermoplastic resin layer can be determined by determining the layer thickness of each thermoplastic resin layer according to the method described below in the layer composition measurement method, and then cutting and removing the thermoplastic resin layer, or by scraping the layer to expose the outermost layer, using infrared spectroscopy (FT-IR method or nano-IR method), gas chromatograph/time-of-flight mass spectrometer (GC-MS), or nuclear magnetic resonance device (NMR). Note that the term "major component" used here refers to a component that is contained in an amount of more than 50% by mass but not more than 100% by mass when the total components in the layer are taken as 100% by mass, and the term "major component" below can be interpreted in the same way.

On the other hand, if it is difficult to identify the composition by the above method while extracting the thermoplastic resin layers constituting the laminated film, the thermoplastic resin layers constituting the laminated film are judged to be "different" by showing different melting points and/or glass transition temperatures in differential scanning calorimetry (DSC). In the present invention, showing different melting points and different glass transition temperatures means that the melting points and glass transition temperatures differ by 0.1°C or more, preferably 2°C or more. In the measurement temperature range of 25°C to 300°C described in the section on differential scanning calorimetry (DSC) in the measurement method described later, there are cases where the thermoplastic resin does not show a glass transition temperature or melting point. In the case where one thermoplastic resin layer shows a glass transition temperature or melting point and the other thermoplastic resin layer does not, it cannot be calculated as a temperature difference, but the thermoplastic resins may be interpreted as being different. DSC measurement can be performed in accordance with JIS-K-7122 (1987), and details will be described later (the same applies to other parameters measured by DSC).

Furthermore, if it is difficult to identify the layers by the above two methods, (3) the brightness of each layer may be different in the image after dyeing when the cross section is observed by transmission electron microscope (TEM), and it may be determined that the layers have different compositions. The layers have different brightnesses when the layer interface due to the brightness difference between each layer can be confirmed in the cross section image observed by transmission electron microscope observation, or when it can be confirmed that the difference in the average brightness of two adjacent layers is larger than any of the standard deviations of the brightness of the adjacent thermoplastic resin layers by the method described in "Layer Interface (Brightness Difference)" below (Examples). Since the brightness difference in the present invention occurs due to scattering of electron beams, crystal diffraction, etc., when the composition of the thermoplastic resin constituting the thermoplastic resin layer differs according to the above-mentioned criteria, the crystallinity and electron density state will differ depending on the type and copolymerization amount of each thermoplastic resin. Therefore, due to the different dyeing state, it is possible to visually recognize each layer as a layer structure with a brightness difference in the cross section image of the laminate film. In other words, the difference in brightness of adjacent layers means that the adjacent thermoplastic resin layers have different compositions.

Representative thermoplastic resins used to form each thermoplastic resin layer of the laminated film of the present invention are shown below, but the thermoplastic resins that can be used in the present invention are not limited to those listed below. For example, polyolefin resins such as polyethylene, polypropylene, poly(1-butene), poly(4-methylpentene), polyisobutylene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, poly(α-methylstyrene), poly(p-methylstyrene), polynorbornene, and polycyclopentene; polyamide resins such as nylon 6, nylon 11, nylon 12, and nylon 66; copolymer resins of vinyl monomers such as ethylene/propylene copolymer, ethylene/vinylcyclohexane copolymer, ethylene/vinylcyclohexene copolymer, ethylene/alkyl acrylate copolymer, ethylene/acrylic methacrylate copolymer, ethylene/norbornene copolymer, ethylene/vinyl acetate copolymer, propylene/butadiene copolymer, isobutylene/isoprene copolymer, and vinyl chloride/vinyl acetate copolymer; acrylic resins such as polyacrylate, polyisobutyl methacrylate, polymethacrylate, polymethyl methacrylate, polybutyl acrylate, polyacrylamide, and polyacrylonitrile. Resins, polyester resins such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, polyether resins such as polyethylene oxide, polypropylene oxide, and polyacrylene glycol, cellulose ester resins such as ethyl cellulose, diacetyl cellulose, triacetyl cellulose, propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose, and nitrocellulose, biodegradable polymers such as polylactic acid and polybutyl succinate, and other polymers such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglycolic acid, polycarbonate, polyketone, polyether sulfone, polyether ether ketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, trichloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinylidene fluoride can be used.

These thermoplastic resins may be used alone or as a polymer blend or polymer alloy of two or more types. By implementing blends or alloys, physical and chemical properties that cannot be obtained from a single type of thermoplastic resin can be obtained. In addition, by arranging a layer containing such a polymer blend or polymer alloy between thermoplastic resin layers with significantly different chemical structures, it is possible to improve interlayer adhesion, which is one of the properties required for a film for molding. Among these, from the viewpoint of rheological properties related to strength, heat resistance, transparency, and lamination, it is preferable that the thermoplastic resin forming the thermoplastic resin layer is selected from polyolefin resins, polyester resins, acrylic resins, and polyamide resins.

It is important that the laminated film of the present invention has three or more consecutive regular arrangements formed of three or more types of thermoplastic resin layers. In addition, from the viewpoint of realizing the desired reflection characteristics while suppressing the complication of the manufacturing process, it is preferable that the types of thermoplastic resin layers constituting the regular arrangement are three types. Hereinafter, when there are three different types of thermoplastic resin layers, each layer is expressed as layer A, layer B, and layer C. Examples of regular arrangements include (ABC)m, (ABCB)m, (ACBC)m, (BACA)m, (ABABC)m, (ACACB)m, (BCBCA)m, (ABCBCB)m, (ACBCBC)m, (BACACA)m, (BCACAC)m, (CABABA)m, and (CBABAB)m (m is a natural number representing the number of repeating units).

In particular, in order to reduce peeling at the interface of different thermoplastic resin layers, it is preferable to have a small number of combinations of adjacent thermoplastic resin layers that form the interface. Specifically, there are three types of interfaces formed from three different thermoplastic resins: A-B interface, B-C interface, and C-A interface. In the above-mentioned regular arrangement, (ABCB)m, (ABCBCB)m, and (CBABAB)m have two types of A-B interface and B-C interface, (ACBC)m, (ACBCBC)m, and (BCACAC)m have two types of A-C interface and B-C interface, and (BACA)m, (BACACA)m, and (BCACAC)m have only two types of A-B interface and A-C interface. Therefore, when considering a combination of thermoplastic resin layers to realize a laminated film without interlayer peeling, in such an embodiment, it is only necessary to consider the interlayer adhesion between one layer of A layer, B layer, and C layer and the other two layers. Therefore, the above-mentioned embodiment is preferable because it makes it easier to form a laminated film with high interlayer adhesion.

Furthermore, in order to improve interlayer adhesion, it is preferable that the difference in compatibility parameters between adjacent thermoplastic resin layers is small. The compatibility parameter referred to here is a parameter related to the energy specific to the thermoplastic resin, and the closer these values are, the easier the resins will mix with each other.

In the laminated film of the present invention, in order to obtain high interlayer adhesion, it is preferable that the difference in absolute values of the solubility parameters (SP values) of adjacent thermoplastic resin layers forming an interface is 1.5 or less. Good compatibility of the thermoplastic resins between adjacent thermoplastic resin layers makes it difficult for delamination to occur in the laminated state.

The compatibility parameter can be estimated by calculation methods such as Hansen, Hoy, and Fedors, but the compatibility parameter of a thermoplastic resin that can be suitably used as an organic polymer material is calculated using the Fedors calculation method, which can calculate based on the repeating structural units of the molecular chain. By using this method, the compatibility parameter of a thermoplastic resin containing a structural unit derived from a copolymerization component can be easily calculated according to the ratio of each structural unit. In the Fedors calculation method, the cohesive energy density and molar molecular volume of the molecule, which depend on the type and number of the substituent, determine the compatibility parameter, and the compatibility parameter δ is estimated according to formula (1). Here, E _coh (cal/mol) represents the cohesive energy, and V represents the molar molecular volume (cm ³ /mol).

In the present invention, the compatibility parameter is a value obtained by rounding off the estimated value calculated based on Fedor's formula to one decimal place. Representative compatibility parameters of thermoplastic resins include cellulose acetate: 11.0, cellulose: 15.6, polyacrylonitrile: 14.8, polyamide: 13.6, polyisobutylene: 7.7, polyethylene: 8.0, polyethylene terephthalate: 10.7, polyvinyl chloride: 10.1, polyvinyl acetate: 9.5, polycarbonate: 9.9, polystyrene: 9.4, polyvinyl alcohol: 12.6, polyphenylene sulfide: 12.5, polybutadiene: 8.3, polypropylene: 8.1, and polymethyl methacrylate: 9.3.

When a thermoplastic resin layer contains multiple thermoplastic resins, the compatibility parameter of the thermoplastic resin layer is determined by multiplying the compatibility parameter value of each thermoplastic resin by the content ratio of the organic polymer material and adding up the results. For example, when polyethylene terephthalate (compatibility parameter: 10.7) and polymethyl methacrylate (compatibility parameter: 9.3) are contained in a ratio of 50:50, the compatibility parameter of the layer is 10.0, which is the intermediate value between the two compatibility parameters.

A typical method for reducing the difference in compatibility parameters between two thermoplastic resin layers is to make the skeletal structure of the thermoplastic resin that is the main component of the two thermoplastic resin layers common. For example, to reduce the difference in compatibility parameters between adjacent thermoplastic resin layers, the main components of these thermoplastic resin layers are made to have a common skeletal structure, and the copolymerization components and the types of alloys/blends are changed, thereby reducing the difference in compatibility parameters between the two thermoplastic resin layers. When two adjacent thermoplastic resin layers have a common chemical structure, strong intermolecular forces act between the adjacent thermoplastic resins, causing interfacial diffusion of polymers, and increasing the thickness region that constitutes the layer interface, which has the effect of increasing adhesion.

It is preferable that the outermost layers of the laminated film of the present invention are both made of the same thermoplastic resin. By having both surface layers made of layers mainly made of the same thermoplastic resin, only one type of thermoplastic resin layer comes into contact with the roll during roll stretching in the manufacturing method described below. Therefore, it is possible to obtain a laminated film in the same film-forming process as when a single-layer film mainly made of the thermoplastic resin is formed, in accordance with the thermal properties of the thermoplastic resin constituting the thermoplastic resin layers arranged on both outermost layers.

Furthermore, it is preferable that the thermoplastic resin constituting the thermoplastic resin layer located on the outermost layer is a layer mainly composed of a crystalline thermoplastic resin. By making the thermoplastic resin layer located on the outermost layer mainly composed of a crystalline resin, for example, when manufacturing a biaxially stretched laminate film by the manufacturing method described below, film formation defects and deterioration of the surface condition due to adhesion to manufacturing equipment such as rolls and clips are reduced, and more uniform stretching is possible due to stress generated during stretching, making it easier to achieve more uniform physical properties and optical properties within the film plane. The crystallinity can be determined by cutting and extracting the thermoplastic resin layer and confirming the presence or absence of melting enthalpy using a differential scanning calorimetry (DSC) device.

It is important that the laminated film of the present invention satisfies the optical properties described below, but in order for the laminated film to exhibit the effect of reflection due to interference, it is preferable to increase the refractive index difference of the thermoplastic resin layer. The refractive index difference here refers to the difference between the average value (in-plane refractive index) of the refractive index in the direction of the main orientation axis and the refractive index in the direction perpendicular to the main orientation axis. The thermoplastic resin constituting the thermoplastic resin layer exhibiting a high refractive index is preferably mainly composed of a crystalline thermoplastic resin that can increase the refractive index by a stretching process. In consideration of the above-mentioned film formability, it is most preferable that the thermoplastic resin constituting the thermoplastic resin layer located at the outermost layer of the laminated film is mainly composed of a crystalline thermoplastic resin. On the other hand, in order to lower the refractive index of the thermoplastic resin layer, the thermoplastic resin constituting the layer is often made amorphous, which is also disadvantageous from the viewpoint of the above-mentioned film formability.

For convenience, the following description will be given on the assumption that, when a thermoplastic resin layer exhibiting crystallinity is included in the thermoplastic resin layers constituting the laminated film, at least layer A is a thermoplastic resin layer exhibiting crystallinity. In this case, among the preferred laminated films having the three types of thermoplastic resin layers with a regular arrangement, (ABCB)mA and (ABCBCB)mA (m is a natural number representing the number of repeating units) are preferred regular arrangement configurations. Furthermore, in consideration of satisfying all of the moldability in post-processing, the film-forming properties, and the reflective effect exhibiting a preferred metallic tone of the laminated film, it is more preferable that layer A is mainly composed of a crystalline thermoplastic resin, and layers B and C are mainly composed of different types of amorphous thermoplastic resins. In other words, it is more preferable that the three types of thermoplastic resin layers constituting the regular arrangement are a combination of crystalline/amorphous/amorphous thermoplastic resin layers.

The crystallinity, semi-crystallineity, and amorphousity mentioned here can all be determined using a differential scanning calorimetry (DSC) device. The thermoplastic resin constituting the crystalline thermoplastic resin layer is characterized by exhibiting three points: the glass transition temperature, the crystallization enthalpy, which is an endothermic peak, and the fusion enthalpy, which is an exothermic peak. Depending on the type of crystalline thermoplastic resin, the glass transition temperature may not fall within the measurement range described below, so here, the degree of crystallinity is determined from the magnitude of the fusion enthalpy. More specifically, in the laminated film of the present invention, crystallinity is defined as a case in which the fusion enthalpy is 10 J/g or more, and semi-crystalline is defined as a case in which the fusion enthalpy is 0.1 J/g or more and less than 10 J/g. Amorphous is defined as a case in which none of these definitions are satisfied. The measurement of the fusion enthalpy can be performed by differential scanning calorimetry (DSC), and the details of the measurement method will be described later.

The combination of crystalline/amorphous/amorphous described here is advantageous in that it provides a laminated film that has good film-forming properties, maintains a favorable reflection effect, and can withstand stretching and heating during molding. For example, even when thermoplastic resin layers with completely different skeletal structures that have a large refractive index difference are laminated to enhance the reflection characteristics, the amorphous thermoplastic resin layer (the layer with the second highest melting enthalpy) disposed between the layers can induce entanglement of molecular chains and reactions between functional groups at the interface, resulting in a laminated film that is less susceptible to interlayer peeling. The amorphous thermoplastic resin layer disposed between the layers can be formed, for example, by melt-extruding a thermoplastic resin exhibiting the desired amorphism from an extruder and laminating it. Alternatively, a method can be used in which a thermoplastic resin with higher crystallinity is extruded and the crystalline phase is melted by heat treatment in the transverse stretching process to form a thermoplastic resin layer exhibiting the desired amorphism.

In the latter case, in particular, the crystalline thermoplastic resin layer needs to have a higher melting point than the amorphous thermoplastic resin layer disposed therebetween. As the thermoplastic resin used for such a crystalline thermoplastic resin layer, from the viewpoints of extrudability, stretchability, versatility, as well as the magnitude of the refractive index of the thermoplastic resin layer when crystallized, which is important for increasing the reflectivity of the laminated film, and the melt viscosity behavior related to lamination accuracy, it is particularly preferable to select from polyethylene terephthalate and its copolymers, polyethylene naphthalate and its copolymers, which have a small number of methylene chains as a polyol component, among the above-mentioned preferred polyester resins. From the above viewpoint, regardless of which of the above methods is adopted as a method for achieving a crystalline/amorphous/amorphous combination, it is particularly preferable that the thermoplastic resin that is the main component of the crystalline thermoplastic resin layer is polyethylene terephthalate or polyethylene naphthalate.

In the laminated film of the present invention, it is preferable that one of the thermoplastic resin layers exhibiting amorphous properties is mainly composed of either acrylic or polyester having an alicyclic structure. The amorphous thermoplastic resin that can be preferably used in the laminated film of the present invention is preferably a thermoplastic resin that has a large refractive index difference with the polyester resin in order to increase the reflectance, and that exhibits melt viscosity characteristics similar to those of the polyester resin in order to obtain a laminated film exhibiting good lamination properties. From the above viewpoint, it is preferable that the thermoplastic resin is selected from acrylic resin and polyester resin exhibiting an alicyclic structure among the above-mentioned thermoplastic resins.

Acrylic resin is an amorphous resin with a refractive index of 1.49, and polyester resin with an alicyclic structure becomes an amorphous resin with a refractive index of 1.52 to 1.55 when it is made into a copolymer type. By laminating thermoplastic resin layers whose main component is an amorphous thermoplastic resin with such a refractive index, the refractive index difference in the regular array can be expanded to a maximum of about 0.25 to 0.30, and a laminated film with a high reflectance that could not be achieved with conventional alternating lamination technology due to interfacial peeling can be realized. The refractive index here refers to the refractive index measured using an Abbe refractometer at 25°C with sodium D line (wavelength 589 nm) as the light source and methylene iodide as the mounting liquid. At this time, the resin can be formed into a sheet by pressing or the like, and then measured.

Examples of polyester resins exhibiting an amorphous alicyclic structure that can be preferably used as the main component of the amorphous thermoplastic resin layer of the laminated film of the present invention include polyester resins copolymerized with structures such as cyclohexanedicarboxylic acid, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, isosorbate, and spiroglycol, which are alicyclic structures.

Although it is not listed as a preferred resin from the viewpoint of stretchability and film-forming property due to its high glass transition temperature, an amorphous polyamide resin can also be used as the main component of the thermoplastic resin layer exhibiting amorphous properties. Examples of amorphous polyamide resins that can be used include polyamide PA12/MACMI (PA12/3,3-dimethyl-4,4-diaminocyclohexylmethane, isophthalic acid), PA12/MACMT (PA12/3,3-dimethyl-4,4-diaminocyclohexylmethane, terephthalic acid), PA MACM 12 (3,3-dimethyl-4,4-diaminocyclohexylmethane, decanedicarboxylic acid or laurolactam), PA MC 12 (PA12, 1,3-bis(aminomethyl)cyclohexane), PA6I/6T, PA6I/6T/MACMI, etc.

As described above, one preferred resin design for enhancing interlayer adhesion is to copolymerize the structural unit contained in the thermoplastic resin that is the main component of one of the adjacent thermoplastic resin layers with the thermoplastic resin that is the main component of the other thermoplastic resin layer. Another example is a method of alloying or blending the thermoplastic resin that is the main component of one of the adjacent thermoplastic resin layers with the thermoplastic resin that is the main component of the other thermoplastic resin layer. These methods are the most commonly used and are the simplest methods, but since components with different basic skeletons coexist in the thermoplastic resin that mainly constitutes the layers, a sea-island structure with the components as islands (domains) may be formed. Also, depending on the dispersion and mixing state of the components with different basic skeletons, the domains of the sea-island structure may become large, increasing the haze and impairing the transparency of the laminated film.

In order to increase the degree of dispersion between thermoplastic resins having different skeletal structures, it is preferable to use a kneading extruder equipped with two or more screws and increase the ratio of the screw rotation speed to the discharge amount during additive kneading, or to change the arrangement of the segments involved in screw kneading so that the screws mesh more deeply with each other to increase the degree of kneading. Alternatively, it is preferable to include an additive with a common skeleton that increases the compatibility of the thermoplastic resins.

Another aspect of resin design that enhances the interlayer adhesion of adjacent thermoplastic resin layers is to react a reactive additive having an unreacted component with the same basic skeleton as the adjacent thermoplastic resin layer with one of the thermoplastic resin layers in advance, thereby containing a component with a common skeleton in both layers and enhancing compatibility. Specifically, the reactive additive is reacted with an unreacted terminal group contained in the thermoplastic resin constituting one of the layers, or with an terminal group contained in an additive previously added to one of the layers, to give a component with the same basic skeleton structure as the adjacent layer and enhance compatibility. As a functional group for realizing such a reaction, for example, when one of the layers contains a carboxyl group terminal, an additive containing a terminal group highly reactive with a carboxyl group, such as a phenol group, an epoxy group, or an amino group, can be added as a reactive additive, and when one of the layers contains an alkoxysilyl group terminal, an additive containing an inorganic filler or a metal component can be added as a reactive additive.

Another aspect of resin design that enhances interlayer adhesion is a formulation in which an adjacent thermoplastic resin layer contains unreacted functional groups that react with unreacted functional group components contained in the other thermoplastic resin layer. In this method, the thermoplastic resins supplied from separate extruders react during the lamination process in the lamination device, so the rheological behavior of the thermoplastic resins that make up each layer is not changed before the lamination process as in the former method, and this is preferable because it is possible to enhance adhesion while suppressing layer disturbance. The combination of functional groups described above can be used as a combination of functional groups that realizes such a reaction.

When the laminated film has four different thermoplastic resin layers (A layer, B layer, C layer, D layer), for example, (ABCD)m, (ABDC)m, (ACBD)m, (ABCCDCB)m, (ABDCDB)m, (ACBDBC)m, (ACDBDC)m, (ADBCBD)m, (ADBCCD)m, (ADBCCD)m, (BACDCA)m, (BADCDA)m, (BCADAC)m, (BCDADC)m, (BDACCAD) )m, (BDCACD)m, (CABDBA)m, (CADBDA)m, (CBADAB)m, (CBDADB)m, (CDABAD)m, (CDBABD)m, (DABCBA)m, (DACBCA)m, (DBACAB)m, (DBCACB)m, (DCABAC)m, (DCBABC)m (m is a natural number representing the number of repeating units), etc., can be used as a laminate film having a regular arrangement.

Even when a laminated film has four types of thermoplastic resin layers with different refractive indices, it is preferable that the number of types of interfaces formed by adjacent thermoplastic resin layers is small and that the difference in refractive index between adjacent thermoplastic resin layers is small in order to provide interlayer adhesion. Therefore, among the above-mentioned regular arrangements, the regular arrangements of (ABCDCB)m and (DCBABC)m (m is a natural number representing the number of repeating units) are preferable. Furthermore, assuming that the melting enthalpy is higher (in other words, the crystallinity is higher) in the order of A layer to D layer, as described above, it is more preferable to have a regular arrangement of (ABCDCB)m (m is a natural number representing the number of repeating units) considering that it is preferable from the viewpoint of film formation that the thermoplastic resin layer arranged on the outermost layer is formed of a crystalline thermoplastic resin.

The types of layers made of thermoplastic resins used in the regular arrangement and the arrangement of the regular arrangement are not limited to those mentioned above, but increasing the number of types of layers increases the number of extruders required for simultaneous extrusion, and increases the number of types of interfaces, making resin design for imparting interfacial adhesion more complex. Furthermore, lamination of thermoplastic resins with different rheological behavior at the same temperature makes lamination more likely to be disrupted. Furthermore, the lamination process for merging the resin layers becomes complicated, so it is not realistic to use five or more types.

The relationship between the film design and optical performance of the laminated film of the present invention is that the presence of multiple regular arrays of similar thicknesses results in high reflectance, and the inclination of the thickness of the regular arrays results in a wide reflection band. Having many types of thermoplastic resin layers with different refractive indices in the regular array allows for more advanced optical design, but the number of types of thermoplastic resins with different skeletons increases. This makes the lamination device more complex, and multiple types of resins with different rheological behavior are laminated, making it easier for lamination disturbances to occur and making film production more difficult. Therefore, it is preferable that the number of types of thermoplastic resin layers constituting the regular array is as small as possible. Specifically, it is preferable that the number of types of thermoplastic resin layers forming the laminated film is four or less, and more preferably three, because this allows the lamination process to be kept from becoming complicated and the wide reflection band and high reflection important in the present invention to be achieved with as few layers as possible.

In the present invention, the laminated film having a certain regular arrangement can be formed by extruding the plurality of thermoplastic resins constituting the regular arrangement from different flow paths using extruders of the same number or more as the types of thermoplastic resins, and forming a laminate using a multi-manifold type feed block or a static mixer, which are known lamination devices. In particular, when used for optical applications, thickness control is very important, so a method using a feed block with fine slits is preferable to obtain the laminated structure of the present invention with high precision and efficiency. When forming a laminate using a slit-type feed block, the thickness and its distribution of each layer can be achieved by changing the length and width of the slit to gradient the pressure loss. Here, the length of the slit refers to the length of the comb teeth that form the flow paths for flowing each thermoplastic resin layer in a certain regular arrangement in the slit plate.

In the laminated film of the present invention, the thermoplastic resin layers constituting the regular arrangement of the laminated film have different crystallinity and electronic state due to different compositions, and therefore also have different refractive indices. Specifically, different refractive indices refer to the difference in refractive index between the three or more resin layers being 0.01 or more. Following this definition, for example, "having three different thermoplastic resin layers" can be interpreted as an embodiment in which there are three types of thermoplastic resin layers, and when two of them are selected and compared for their refractive index values, there is a difference of 0.01 or more between them. By having different refractive indices for each thermoplastic resin layer, it becomes possible to express optical interference reflection based on optical theory, which can reflect light of a specific wavelength based on the relationship between the difference in refractive index between each layer and the layer thickness.

Specifically, when the thicknesses of the thermoplastic resin layers adjacent to each other across the interface are _dX and _dY (X, Y = A, B, C...), and the refractive index difference between the adjacent layers is Δn = | _nY - _nX |, the reflected light wavelength (λ) is determined according to formula (2), and the reflectance (R) is determined according to formula (3) based on the refractive index difference _ΔnX between the adjacent layers ( _θX and _θY refer to the angle of incidence on the layer viewed from the direction perpendicular to the surface of the laminated film, and the angle of incidence when entering the adjacent layer. k is an arbitrary natural number.). Here, when thermoplastic resins having the same refractive index are used for the adjacent layers, the numerator of formula (3) representing the reflectance is 0, particularly for light incident in the direction perpendicular to the surface, which means that no interference reflection occurs at the interface.

The laminated film of the present invention has three or more consecutive layers of three or more different thermoplastic resins in a regular regular arrangement, which makes it easier to generate interference reflection and increases the reflectance of the laminated film. From the above viewpoint, the number of layers forming the regular regular arrangement is more preferably 100 layers or more, and even more preferably 300 layers or more. The more layers that make up the regular regular arrangement, the stronger the interference reflection can be, but a total of 900 layers or less is realistic because of the possibility of increased manufacturing costs due to larger manufacturing equipment, deterioration of the uniformity of the laminated film in the width direction due to lamination disorder and width direction inclination of the lamination ratio due to the complexity of the lamination process, and deterioration of handleability due to an increase in film thickness.

In the laminated film of the present invention, the wide reflection band can be achieved by continuously sloping the layer thickness of the laminated film according to formula (2). In addition, the reflection wavelength band can be expanded and the reflectance can be increased by increasing the number of layers. In this case, by making the wavelength band Π of the laminated film of the present invention the entire visible light range, a metallic film with good adhesion can be obtained with a lower number of layers and a thinner film than before. In particular, in applications for automobiles, home appliances, and electronic devices, it is possible to impart metallic optical properties to the molded body by performing insert molding or in-mold molding, but in conventional laminated films, when the thickness of the laminated film changes due to local stretching caused by molding, there was a problem that the wavelength band shifts due to thinning and the metallic tone is lost. By realizing a laminated film capable of wideband reflection having a reflection band in the long wavelength range in addition to the visible light range with the laminated film of the present invention, even if the film stretches after molding, it is easy to maintain the metallic tone.

In the laminated film of the present invention, thermoplastic resins with different skeletal structures may be laminated in order to increase the difference in refractive index between a layer exhibiting a high refractive index and a layer exhibiting a low refractive index in order to achieve a desirable reflectance that exhibits a metallic tone. However, generally, when resins with different skeletal structures and a large difference in compatibility parameters are laminated together, the interlayer adhesion is poor and peeling occurs. Even in the conventional known examples, there are many descriptions and examples of combinations of thermoplastic resins with different skeletal structures to exhibit a high reflectance, and descriptions of the optical properties of the resulting laminated film. However, although such laminated films satisfy the optical properties, interlayer peeling occurs, making it difficult to put them into practical use in many cases.

In order to maintain the desirable metallic reflectance before and after molding, it is important that the first laminate film of the present invention has an average reflectance of 35% to 100% at wavelengths of 400 nm to 800 nm, and that the change in average reflectance ΔR1 at wavelengths of 400 nm to 800 nm when the film is stretched 30% at 100°C in the direction of the main orientation axis and in the direction perpendicular to the main orientation axis is 0.1% to 20%.

The average reflectance referred to here is the value obtained by averaging the reflectance from wavelengths 400 nm to 800 nm when measuring at a sampling pitch of 1 nm according to the "reflection spectroscopy measurement" in the measurement method described below. The main orientation axis direction of the film refers to the direction in the film plane that has the maximum refractive index. The direction of the maximum refractive index in the film can be determined by determining the slow axis direction using a phase difference measurement device (birefringence measurement device) or the like.

From the above viewpoint, it is also preferable that the first and second laminate films of the present invention have an average reflectance of 35% or more and 100% or less at wavelengths of 400 nm to 800 nm, and that the average reflectance change ΔR2 at wavelengths of 400 nm to 800 nm when stretched 50% at 100°C in the main orientation axis direction and in the direction perpendicular to the main orientation axis is 0.1% or more and 20% or less.

The average reflectance of 35% or more and 100% or less in the wavelength range of 400 nm to 800 nm indicates that the laminated film reflects visible light and exhibits a desirable metallic color tone. If the average reflectance in the above wavelength range is 50% or more and 100% or less, the metallic glossiness is more strongly expressed, which is preferable in terms of enhancing the design. On the other hand, if the average reflectance in the above wavelength range is less than 35%, a sufficient reflection effect cannot be obtained, and the desirable metallic color tone may not be expressed, or undesirable color changes such as color unevenness may occur. The average reflectance referred to here is the value obtained by averaging the reflectance from wavelengths of 400 nm to 800 nm when measured at a sampling pitch of 1 nm according to the "reflection spectroscopy measurement" in the measurement method described below.

Heat molding methods such as vacuum molding, pressure molding, vacuum pressure molding, press molding, and plug-assist molding are used to mold the components, but all of these molding methods involve a process in which the film is heated to a high temperature in a preheating process using an infrared heater or the like before molding. Stretching the film by 30% at 100°C in the main orientation axis direction and in the direction perpendicular to the main orientation axis mimics the heating and elongation of the laminated film during such molding. In other words, when the film is stretched by 30% at 100°C in the main orientation axis direction and in the direction perpendicular to the main orientation axis, the average reflectance change ΔR1 at wavelengths of 400 nm to 800 nm is 0.1% to 20%, indicating that the laminated film of the present invention can withstand the stretching and heating during molding and maintain a favorable metallic color tone and gloss even after molding and stretching.

Stretching the film by 50% at 100°C in the direction of the main orientation axis and in the direction perpendicular to the main orientation axis mimics the heating and elongation of the film in processes that require higher moldability, such as deep drawing. In other words, when the film is stretched by 50% at 100°C in the direction of the main orientation axis and in the direction perpendicular to the main orientation axis, the average reflectance change ΔR2 at wavelengths of 400 nm to 800 nm is 0.1% to 20%, which indicates that the laminated film of the present invention has high moldability and optical performance with reduced tearing and insufficient tracking, even in processes that require high moldability, such as deep drawing.

The smaller the average reflectance changes ΔR1 and ΔR2, the less the change in color tone before and after molding. Therefore, the smaller the value, the better, and it is more preferable for both to be between 0.1% and 15%. If the average reflectance changes ΔR1 and ΔR2 are 20% or more, the difference in reflectance before and after molding will be too large, which may cause the color tone of the laminated film to change, or cause color loss or color unevenness in the laminated film, which may be disadvantageous when used for molding purposes.

In the present invention, methods for setting the average reflectance at wavelengths of 400 nm to 800 nm within the above-mentioned preferred range include adjusting the number of layers, the layer structure, and the components of each layer. More specifically, methods include increasing the number of regular arrangements to increase the number of layers that reflect the desired wavelength band, making the gradient of the layer thickness distribution gentler (reducing the gradient), and selecting a combination of thermoplastic resins that are the main components of layers A and C so that the in-plane refractive index difference is high.

The gradient here refers to the ratio of the maximum layer thickness to the minimum layer thickness (maximum layer thickness/minimum layer thickness) in the portion of the layer thickness distribution of each thermoplastic resin layer that shows a monotonically increasing distribution. Note that when multiple thermoplastic resin layers have a monotonically increasing layer thickness distribution, the average value of each thermoplastic resin layer is used as the gradient.

Methods for setting ΔR1 and ΔR2 in the above-mentioned preferred ranges include a method for setting the average reflectance at wavelengths of 400 nm to 800 nm in the above-mentioned preferred range, a method for adjusting the stretching ratio and discharge amount, and a method for laminating layers so that the lamination ratio (A/B) of layer A to layer B and the lamination ratio (C/B) of layer C to layer B are not less than 0.5 so that the preferred refractive index difference between layer A and layer C can be maintained even after stretching, and a method for setting the maximum difference in the above-mentioned solubility parameters (SP values) in each thermoplastic resin layer to 2.0 or less can be used. In terms of improving moldability, there are also methods such as using an unstretched film to prevent overstretching during molding, and using a resin containing a copolymer component in some of the thermoplastic resin layers to suppress oriented crystallization during molding.

Examples of the copolymerization components that can be used include adipic acid, cyclohexanedimethanol, bisphenol A ethylene oxide, spiroglycol, isophthalic acid, isosorbide, cyclohexanedicarboxylic acid, neopentyl glycol, polyethylene glycol 2000, m-polyethylene glycol 1000, m-polyethylene glycol 2000, m-polyethylene glycol 4000, m-polypropylene glycol 2000, bisphenylethylene glycol fluorene (BPEF), fumaric acid, and acetoxybenzoic acid. By including such copolymerization components, oriented crystallization of the laminated film during molding is suppressed, and the stretchability of the laminated film can be increased.

When polyethylene terephthalate is used as the main component of the thermoplastic resin layer, spiroglycol is particularly preferred among the copolymerization components. Since the difference in glass transition temperature between spiroglycol and polyethylene terephthalate is small when copolymerized, overstretching during molding is unlikely to occur, and delamination is unlikely to occur. In addition, when polyethylene glycol is copolymerized, interlayer adhesion is improved with an increase in hydrophilicity, and the glass transition temperature can be effectively lowered, improving co-stretchability. In addition, in the laminated film of the present invention, since the interlayer adhesion is good by adopting the above-mentioned embodiment, if one of the three or more types of thermoplastic resin layers is designed to suppress oriented crystallization during molding, the other types of thermoplastic resin layers will also follow and have good stretchability.

From the viewpoint of maintaining the preferable metallic reflectance after molding as well as before molding, it is important that the second laminate film of the present invention has a chroma C* of 0.1 to 20 and a chroma change ΔC* of 0.1 to 15% when stretched 30% at 100°C in the main orientation axis direction and in the direction perpendicular to the main orientation axis. More preferably, the chroma C* is 0.1 to 15 and a chroma change ΔC* of 0.1 to 10% when stretched 30% at 100°C in the main orientation axis direction and in the direction perpendicular to the main orientation axis. It is preferable that the first laminate film of the present invention also satisfies the above requirements.

Saturation C* is one of the three attributes of color and is a measure of color vividness. If the saturation C* is greater than 20, the metallic design will be inferior due to coloring, and the color will look unnatural. If the change in saturation ΔC* (hereinafter sometimes simply referred to as saturation change ΔC*) when stretched 30% at 100°C in the main orientation axis direction and in the direction perpendicular to the main orientation axis is 15% or more, the change in saturation C* due to stretching is large, and the laminated film may suffer from defects such as color unevenness, color loss, and unwanted color changes.

One method for setting the chroma C* and chroma change ΔC* within the above-mentioned preferred ranges is to design a film with high reflectance and wide reflection band. Specifically, one method is to design a film with a regular arrangement composed of three different types of thermoplastic resin layers, with the stacking ratio (A/B) of A layer to B layer in the regular arrangement being 0.50 or more, and the stacking ratio (C/B) of C layer to B layer being 0.90 or more, and the average reflectance at wavelengths of 400 nm to 800 nm being 35% or more. Another method is to design a film with an average reflectance at wavelengths of 400 nm to 800 nm being 35% or more, and with the average reflectance at wavelengths of 400 nm to 800 nm being R [%] and the deviation of the reflectance being σ [%], the percentage of σ/R being 10.0% or less. Other methods include adjusting the number of layers, layer structure, and components of each layer. More specifically, examples include increasing the number of regular arrangements to increase the number of layers that reflect the visible light reflection band, creating a preferred layered structure with the aforementioned (ABCB)m regular arrangement (the layer arrangement in parentheses, m is a natural number representing the number of repeating units), using an amorphous thermoplastic resin in one of the thermoplastic resin layers, and not mixing resins with different properties (crystalline and amorphous) in the B layer.

Another method for setting the chroma C* and chroma change ΔC* within the above-mentioned preferred ranges is to set the average reflectance at wavelengths of 400 nm to 800 nm to less than 10% and the average reflectance at wavelengths of 900 nm to 1200 nm to 70% or more. Such optical performance can be achieved by having a regular arrangement composed of three different types of thermoplastic resin layers, with the layer thickness distribution being such that, except for both outermost layers and the intermediate layer, the layer thickness monotonically increases from the outermost surface on one side to the intermediate layer, and monotonically decreases from the intermediate layer to the other side.

In the laminated film of the present invention, it is preferable that, in the wavelength range of 300 nm to 2600 nm, the reflection bandwidth of the widest reflection band Π where the reflectance is 20% or more continuously over 100 nm or more is λ [nm], the average reflectance in the reflection band R [%], and the film thickness t [μm], (λ·R)/t is 820 to 1400. Here, the judgment is made using the reflection spectrum obtained by measuring at 1 nm pitch using a spectrophotometer and performing 10-point averaging in the reflectance/reflection spectrum measurement described later in the examples. As will be described in detail later, reflectance data from 295 nm to 2605 nm is obtained in the measurement using a spectrophotometer, and the reflection spectrum data from 300 nm to 2600 nm can be obtained by averaging the data from 10 consecutive points.

The widest reflection band Π where the reflectance is 20% or more continuously over 100 nm or more will be described with reference to Figures 1 to 4. In Figures 1 to 4, the reference characters 1 to 4 respectively indicate the reflection spectrum, reflection band Π, reflection bandwidth λ, and average reflectance R, and the reflection spectrum indicated by reference character 1 is a spectrum obtained by applying a 10-point averaging process. As shown in Figures 1 and 2, the wavelength band Π refers to the wavelength band located on the longest wavelength side when there are multiple wavelength bands in the wavelength band of 300 nm to 2600 nm inclusive that show a reflectance of 20% or more continuously over 100 nm or more in the reflection spectrum subjected to the averaging process. Figure 2 illustrates the average reflectance in a reflection band shape different from that in Figure 1. Also, as shown in Figure 3, if the reflection wavelength band includes even a part of an area showing a reflectance of less than 20%, the wavelength band on the longest wavelength side that shows a reflectance of 20% or more continuously over 100 nm is defined as Π, with the area as the boundary. Also, as shown in FIG. 4, if there is a wavelength band on the long wavelength side that exceeds 2600 nm and shows a reflectance of 20% or more, the wavelength band is defined as Π if the portion included in the wavelength band from 300 nm to 2600 nm shows a reflectance of 20% or more over 100 nm or more.

The reflection bandwidth in the wavelength band Π is expressed as λ [nm], and the average reflectance in the reflection band R [%]. λ·R is expressed by the area of the shaded area in Figures 1 to 4. In reality, the area of this area represents the broadband and high reflectance performance of the laminate film, but in the case of the laminate film of the present invention, even if the laminate film is produced through the same lamination process, the wavelength band shifts depending on the thickness of the laminate film. Therefore, in order to more accurately represent the characteristic of the laminate film of the present invention, "the effect of high reflectance and wide reflection band that exhibits a metallic tone even in a thin film after molding," it is effective to divide the area λ·R by the thickness t. By such a procedure, the effect of the change in wavelength bandwidth due to the thickness of the laminate film can be canceled out, and the effect of high reflectance and wide reflection band based on the configuration of the laminate film can be represented.

For example, in the case of a laminated film that uniformly reflects 90% of the wavelength band from 800 nm to 1200 nm, the area (λ·R) is (1200-800) nm x 90%, or 36,000, by simple calculation. However, if the thickness of the laminated film is halved, the wavelength band becomes 400 nm to 600 nm, so the area becomes (600-400) nm x 90%, or 18,000, and the area changes even for laminated films with the same laminate structure. Therefore, the effect of widening the reflection band and increasing the reflectance is reflected not only by the laminated film structure but also by the thickness. Therefore, if the former film thickness is divided by t μm and the latter by half the thickness t/2 μm, both become (λ·R)/t = 18,000/t, and it becomes possible to compare the effects of widening the reflection band and increasing the reflectance based on the laminated film structure, regardless of the thickness of the laminated film, even between laminated films that reflect different wavelength bands.

(λ·R)/t of 820 or more and 1400 or less indicates that the laminate film has both high reflectivity and wideband reflection while having a low number of layers (thin film), which cannot be achieved by conventional technology, especially by a laminate film of (AB)m (m is a natural number representing the number of repeating units) in which two types of thermoplastic resin layers are alternately laminated. (λ·R)/t of 820 or more indicates that the thickness or number of layers is small while it is a laminate film for obtaining a certain high reflectivity and high reflection band, and indicates that a laminate film suitable for applications requiring suppression of the enlargement of the manufacturing equipment and greater moldability such as deep drawing molding can be obtained. Furthermore, the small thickness of the laminate film also improves processability such as handling during post-processing. On the other hand, (λ·R)/t of 1400 or less means that the realization of high reflectivity and wide reflection band is achieved with a smaller number of layers than conventional alternating lamination technology, taking into account the interlayer adhesion and the thickness of the laminate film. To achieve high reflectance and a wide reflection band with a small number of layers, it is necessary to increase the refractive index difference between the thermoplastic resin layers, and therefore it is essential to laminate thermoplastic resin layers made of thermoplastic resins with completely different skeletal structures. As a result, when a laminated film is formed, the interlayer adhesion may be poor. From the above viewpoint, a more preferable range for (λ·R)/t is 950 or more and 1200 or less.

To satisfy these relationships, methods include adjusting the number of layers, layer structure, and components of each layer. More specifically, it is possible to use a combination of resins that increases the maximum refractive index difference, increase the number of layers that reflect the visible light reflection band by increasing the number of regular arrangements, use a preferred layer structure with the aforementioned (ABCB)m regular arrangement (layer arrangement in parentheses, m is a natural number representing the number of repeating units), and not mix resins with different properties (crystalline and amorphous) into the B layer.

The laminated film of the present invention may contain light absorbers (ultraviolet absorbers, dyes, pigments, heat absorbers), antioxidants, light stabilizers, quenchers, heat stabilizers, weather stabilizers, organic lubricants, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, flame retardants, etc., to the extent that the film's inherent properties are not deteriorated. In particular, since some thermoplastic resins may absorb high-energy ultraviolet light and accelerate deterioration, it is preferable to contain an ultraviolet absorber for the purpose of suppressing photodegradation by competing reactions. Furthermore, the light absorber itself may be affected by deterioration due to heat and oxygen in the resin extrusion process, and photodegradation due to reaction with ultraviolet light and oxygen. Therefore, it is preferable to add an antioxidant for the former, and a light stabilizer or quencher for the latter, both as additives, to the thermoplastic resin layer that may be subject to deterioration.

The laminated film of the present invention preferably has a peeling rate of 10% or less in an adhesion test based on the cross-cut method specified in JIS K 5600-5-6:1999. Hereinafter, the "adhesion test based on the cross-cut method specified in JIS K 5600-5-6:1999" is sometimes referred to as the peeling test, and the "peeling rate of the squares in the adhesion test based on the cross-cut method specified in JIS K 5600-5-6:1999" is sometimes simply referred to as the peeling rate. Peeling of the laminated film is thought to occur both due to cohesion/material failure, in which breakage occurs inside each thermoplastic resin and peeling occurs, and interfacial failure, in which peeling occurs at the interface between thermoplastic resin layers, and the cross-cut test can capture peeling caused by both. Both peelings are phenomena that should not occur when the laminated film is used for a long period of time. A peeling rate of less than 10% in the cross-cut test indicates that the laminated film has long-term reliability, or in other words, that interlayer peeling is unlikely to occur even in post-processing such as molding.

If the peeling rate exceeds 10%, destruction will occur from the laminate film interface during long-term use. For example, in the processing step, lifting due to peeling will occur at the interface while the film is transported on a roll, or cracks will occur at the cross section during the cutting step, causing peeling at the laminate film interface due to the peel strength being too high when a protective film provided at a different position from the laminate film is peeled off. In applications where repeated folding processes are performed, the occurrence of lifting at the interface will cause problems such as the loss of physical properties and optical characteristics derived from the laminate film. From the above perspective, the peeling rate is more preferably 3% or less, and most preferably 0%. Theoretically, the lower limit of the peeling rate is 0%.

As a method for achieving a peel rate of less than 10% or within the above-mentioned preferred range in the cross-cut test, it is possible to use a method of adjusting the resin design and film design to increase interlayer adhesion, such as by reducing the difference in compatibility parameters as described above.

The laminated film of the present invention has better visible light reflection properties than conventional laminated films, and can therefore be used favorably for decorative purposes that exhibit a metallic or colored metallic look. That is, the decorative film of the present invention is made using the laminated film of the present invention. For example, in automotive applications, the trend toward making electric vehicles lighter is accelerating, and parts that have traditionally been made of metal are increasingly being made of resin. By using the decorative film of the present invention, it is possible to give a metallic look by integrally molding the film with a molded resin in front grilles, window moldings, emblems, etc. In addition, the decorative film of the present invention can also be used for interior components around panels to give a sense of luxury. In addition, the decorative film of the present invention can also be used for back decoration of home appliances and electronic devices, half-mirror-like films, etc.

It can be used by post-attaching to a product, or by in-mold or insert molding into a molded body. In other words, the molded body of the present invention is made using the laminate film of the present invention or the decorative film of the present invention.

Next, a preferred method for producing the laminated film of the present invention will be described below. Of course, the present invention is not to be interpreted as being limited to the example described.

The thermoplastic resins constituting each thermoplastic resin layer of the laminated film are prepared in the form of pellets or the like. If necessary, the pellets are dried in hot air or under vacuum and then fed to separate extruders. If additives are contained in the thermoplastic resin, powder, granules, or liquid additives may be kneaded and dispersed during the main extrusion process, or master pellets in which additives have been dispersed in the thermoplastic resin in advance may be fed. In the extruder, each thermoplastic resin is heated and melted to above its melting point and extruded while making the extrusion amount uniform with a gear pump or the like, and foreign matter and denatured resins are removed through a filter or the like. These molten thermoplastic resins are laminated into the desired layer configuration by a lamination device, and then discharged from a die in the form of a sheet. The molten sheet-like material discharged from the die is then cooled and solidified on a cooling body such as a casting drum to obtain a cast sheet. At this time, it is preferable to use a wire-shaped, tape-shaped, needle-shaped, or knife-shaped electrode to bring the material into contact with a cooling body such as a casting drum by electrostatic force and rapidly solidify it. Also preferred is a method in which air is blown from a slit-shaped, spot-shaped, or planar device to bring the material into contact with a cooling body such as a casting drum and rapidly solidify it, or a method in which the material is rapidly solidified by bringing the material into contact with a cooling body using a nip roll. As an auxiliary method, a liquid with good wettability, such as liquid surfactant water or liquid paraffin, can be applied to the surface of the casting drum to provide adhesion.

The thermoplastic resins forming the three different thermoplastic resin layers constituting the laminated film are sent out from different flow paths using three or more extruders, and are fed into a multi-layer lamination device before being extruded in sheet form. As the multi-layer lamination device, a multi-manifold die, a feed block, a static mixer, etc. can be used, but in particular, in order to efficiently obtain a multi-layer laminate structure, it is preferable to use a feed block having fine slits. When such a feed block is used, the device does not become extremely large, so the amount of foreign matter generated due to thermal deterioration is small, and high-precision lamination is possible even when the number of layers is extremely large. In addition, the lamination accuracy in the width direction is significantly improved compared to conventional technology. In addition, with this device, the thickness of each layer can be adjusted by the shape (length, width) of the slit, so that any layer thickness can be achieved. The molten multi-layer laminate sheet formed in the desired layer configuration in this way is guided to the die, and a cast sheet is obtained as described above.

Then, it is preferable to biaxially stretch the obtained cast sheet in the longitudinal direction and the width direction. The stretching may be performed biaxially in succession or simultaneously. Furthermore, the sheet may be re-stretched in the longitudinal direction and/or the width direction. Here, the longitudinal direction refers to the running direction of the film, and the width direction refers to the direction perpendicular to the longitudinal direction within the film plane.

First, the case of sequential biaxial stretching will be described. Here, stretching in the longitudinal direction refers to uniaxial stretching for giving the sheet longitudinal molecular orientation, which is usually performed by the difference in peripheral speed of the rolls, and may be performed in one stage or in multiple stages using multiple pairs of rolls. The stretching ratio varies depending on the type of resin, but is usually preferably 2.0 to 10 times. For example, when using polyethylene terephthalate or polyethylene naphthalate, which is a thermoplastic resin that forms a thermoplastic resin layer exhibiting crystallinity and is preferably used in the laminated film of the present invention, 2.0 to 7.0 times is particularly preferably used. In addition, the stretching temperature is preferably set within the range of the glass transition temperature to the glass transition temperature + 100°C of the thermoplastic resin layer having the highest glass transition temperature among the thermoplastic resin layers constituting the laminated film. If strong orientation is performed in the longitudinal stretching process, neckdown occurs in the film width direction, and sufficient film width cannot be obtained, and thickness unevenness and transmission spectrum unevenness in the longitudinal and/or width directions after width direction stretching may become large.

The uniaxially stretched laminate sheet thus obtained is subjected to a surface treatment such as corona treatment, frame treatment, or plasma treatment as necessary, and then an easy-adhesion layer having functions such as easy slippage, easy adhesion, and antistatic properties is applied by in-line coating. In the in-line coating process, the easy-adhesion layer may be applied to one side of the laminate film, or to both sides of the laminate film simultaneously or one side at a time.

Then, the uniaxially stretched laminated sheet is stretched in the width direction. Stretching in the width direction refers to stretching to give the sheet a width direction orientation, and is usually performed by using a tenter to convey the sheet while holding both ends in the width direction with clips. The stretching ratio varies depending on the type of resin, but is usually preferably 2.0 to 10 times. For example, when using polyethylene terephthalate or polyethylene naphthalate, which are thermoplastic resins that form the crystalline thermoplastic resin layer preferably used in the laminated film of the present invention, a stretching ratio of 2.0 to 7.0 times is particularly preferred. In addition, the stretching temperature is preferably the glass transition temperature to the glass transition temperature + 120°C of the resin with the highest glass transition temperature among the resins that make up the laminated film.

The laminated film thus biaxially stretched is then heat-treated in a tenter at a temperature equal to or higher than the stretching temperature and equal to or lower than the melting point of the thermoplastic resin layer with the highest melting point among the thermoplastic resin layers constituting the laminated film, and is then uniformly and slowly cooled, cooled to room temperature, and wound up. If necessary, a relaxation treatment may be performed in the longitudinal and/or transverse directions when slowly cooling after heat treatment in order to impart thermal dimensional stability.

Next, the case of simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the obtained cast sheet may be subjected to a surface treatment such as corona treatment, frame treatment, or plasma treatment as necessary, and then functions such as easy slip, easy adhesion, and antistatic properties may be imparted by in-line coating. In the in-line coating process, the easy adhesion layer may be applied to one side of the laminated film, or may be applied to both sides of the laminated unit simultaneously or one side at a time.

Next, the cast sheet is introduced into a simultaneous biaxial tenter, and conveyed while holding both ends of the sheet in the width direction with clips, and is stretched simultaneously and/or stepwise in the longitudinal and width directions. The simultaneous biaxial stretching machine can be of the pantograph type, screw type, drive motor type, or linear motor type, but the drive motor type or linear motor type is preferred, since it can change the stretching ratio at any desired position and can perform relaxation treatment at any desired location. The stretching ratio varies depending on the type of resin, but usually, an area ratio of 6.0 to 50 times is preferred, and when using polyethylene terephthalate or polyethylene naphthalate, which is a thermoplastic resin that forms the crystalline thermoplastic resin layer preferably used in the laminated film of the present invention, an area ratio of 8 to 30 times is particularly preferred. The stretching speed may be the same or different in the longitudinal and width directions. The stretching temperature is preferably the glass transition temperature to glass transition temperature + 120°C of the thermoplastic resin layer with the highest glass transition temperature among the thermoplastic resin layers that constitute the laminated film.

The sheet thus simultaneously biaxially stretched is preferably subsequently heat-treated in a tenter at a temperature equal to or higher than the stretching temperature and equal to or lower than the melting point in order to impart flatness and dimensional stability. During this heat treatment, it is preferable to instantly relax the sheet in the longitudinal direction immediately before and/or immediately after entering the heat treatment zone in order to suppress the distribution of the main orientation axis in the width direction. After being heat-treated in this manner, the sheet is uniformly cooled slowly, cooled to room temperature, and wound up. If necessary, the sheet may be relaxed in the longitudinal direction and/or width direction when being cooled slowly from the heat treatment. The sheet may also be relaxed in the longitudinal direction immediately before and/or immediately after entering the heat treatment zone.

The laminated film obtained in this manner is trimmed to the required width using a winding device, and is wound up in a roll to prevent wrinkles from forming. In addition, embossing may be applied to both ends of the film during winding to improve the appearance of the roll.

The thickness of the laminated film of the present invention is not particularly limited, but is preferably 10 μm or more and 100 μm or less. Taking into account the trend toward thinner functional films, it is preferably 70 μm or less, and more preferably 50 μm or less. Although there is no lower limit, in order to ensure stable roll winding and film formation without tearing, a thickness of 10 μm or more is practically preferable.

There are no particular limitations on the method for adjusting the thickness of the laminated film, but since it is preferable to adjust the thickness without varying the stretch ratio in the conveying direction and width direction, it is preferable to adjust it by increasing or decreasing the take-up speed of a cooling body such as a casting drum. In order to suppress the film width shrinkage that occurs at this time, it is also preferable to appropriately adjust the gap between the die and the cooling body. If the film width cannot be kept constant, for example, the stretch ratio in the width direction can be made constant by adjusting the distance between the clips in the tenter.

In addition, the outermost surface of the laminated film of the present invention may be laminated with a hard coat layer mainly composed of a curable resin in order to add functions such as scratch resistance, dimensional stability, and adhesiveness/adhesion. When the laminated film is transported by roll-to-roll for mounting on a product, scratches on the laminated film surface due to friction between the roll and the film can be prevented. Furthermore, even if the resin oligomer components in the laminated film and various additives that can be added to the laminated film may bleed out during high-temperature heat treatment, by providing a hard coat layer on the outermost surface, the hard coat layer with high crosslinking density can exhibit a precipitation suppression effect. In addition, by laminating a curable resin layer, it is possible to suppress dimensional changes in the film due to heat treatment, and it is possible to suppress an increase in film thickness due to heat shrinkage and the accompanying changes in optical properties such as the transmission spectrum of the laminated film. On the other hand, optically, it is preferable to provide a thermosetting resin layer that has a refractive index lower than the refractive index of the thermoplastic resin layer that shows the crystallinity of the laminated film surface, because the difference in refractive index with the air interface is reduced, thereby suppressing surface reflection and increasing the reflectance of the entire laminated film.

In addition to the hard coat layer, other functional layers may be formed, such as an abrasion-resistant layer, an anti-reflection layer, a color correction layer, an ultraviolet absorbing layer, an adhesive layer, a gas barrier layer containing metal oxides, a printing layer, etc. These layers may be single or multiple, and one layer may have multiple functions.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Each characteristic was measured by the following methods.

(Methods for measuring characteristics and evaluating effects)
The methods for measuring the various characteristics and evaluating the effects in the present invention are as follows.

(1) Differential Scanning Calorimetry (DSC)
A differential scanning calorimeter EXSTAR DSC6220 manufactured by Hitachi High-Technologies Corporation was used. Measurements and temperature readings were performed in accordance with JIS-K-7122 (1987). Specifically, when about 5 mg of a sample was placed on an aluminum tray and heated from 25°C to 300°C at a rate of 10°C/min, the intersection of the baseline when the temperature was raised from room temperature and the tangent at the inflection point of the step transition portion was taken as the glass transition temperature Tg (°C), and the peak top at the time of crystal melting was taken as the melting point. Furthermore, after heating, the sample was quenched with liquid nitrogen, and when the temperature was raised further under the same conditions, the area of the endothermic peak (melting point) confirmed at the highest temperature side was obtained by integration from the baseline, and this endothermic peak (melting point) area was taken as the fusion enthalpy Tm (J/g).

(2) Layer structure The layer thickness distribution of the laminated film was determined by observation of a sample sliced using an ultramicrotome with a transmission electron microscope (TEM). Specifically, a transmission electron microscope JEM-1400 Plus (manufactured by JEOL Ltd.) was used to observe the cross section of the laminated film under conditions of an acceleration voltage of 100 kV, and a cross-sectional image was obtained to measure the layer structure (number of layers, regular arrangement, layer thickness distribution) and each layer thickness. In order to obtain a large brightness difference between each layer, a dyeing technique using an electronic dye (RuO ₄ , etc.) was used. In addition, in accordance with the thickness of each layer, when the thin film layer thickness is less than 100 nm, a direct magnification of 40,000 times was used, when the thin film layer thickness is 100 nm or more and less than 500 nm, a direct magnification of 20,000 times was used, and when the thin film layer thickness is 500 nm or more, observation was performed at a direct magnification of 1,000 to 10,000 times depending on the thickness, and the layer thickness distribution was analyzed. Based on the brightness difference of the obtained image, the number of layers, regular arrangement, layer thickness of each layer, layer thickness distribution, lamination ratio based on layer thickness, and gradient were each determined. The lamination ratio was calculated by focusing on the regular arrangement of the portions excluding the outermost layer A, and the lamination ratio of the other thermoplastic resin layers was calculated based on the thermoplastic resin layer B. (3) In the layer thickness distribution of each layer thickness obtained according to the layer interface (brightness difference), the maximum layer thickness was determined as the thickest layer thickness in the portion where the layer thickness shows a monotonous increase, and the thinnest layer thickness was determined as the gradient.

(3) Layer interface (brightness difference)
(2) The cross-sectional image obtained in the transmission electron microscope observation was converted to a compressed image file (JPEG) format, and position-luminance data was obtained by line profile along the thickness direction of the laminated film using ImagePro-10 (sold by Hakuto Co., Ltd.). Then, a five-point moving average process was performed on the profile obtained by plotting the relationship between position and luminance using a spreadsheet software (Microsoft Corporation "Excel" (registered trademark) 2016). The averaging process was performed by performing an averaging process of luminance on five consecutive measurement positions, changing the position one point at a time, and continuously processing the same calculation, thereby obtaining an averaged position-luminance profile. In the obtained averaged position-luminance profile, the position surrounded by the inflection points where the slope changes from positive to negative, or from negative to positive, was determined to be one layer. For each layer obtained by this method, position-luminance data was then obtained in the planar direction (direction perpendicular to the thickness direction) of the laminated film. After calculating the average and standard deviation of the luminance obtained for each layer, if the difference between the average luminance values of two adjacent layers was greater than either of the standard deviations of the luminance values of the adjacent thermoplastic resin layers, the two adjacent layers were determined to be different. In addition, the difference (distance) between the positions of the inflection points was calculated as the layer thickness of each layer.

(4) Reflection Spectrum Measurement A sample was cut out from the center of the laminated film in the width direction to a 4 cm square, and one side of the laminated film was subjected to back black treatment using black lacquer spray. In the back black treatment, three coats were applied to make it completely opaque to light. A spectrophotometer U-4100 manufactured by Hitachi High-Tech Science was used, and an attached aluminum oxide plate was fixed as a reflecting member to the opening on the back of the integrating sphere. In addition, as an absolute reflectance measurement unit using specular reflection, an attached 12° regular reflection attachment (P/N 134-0104) was installed just before the integrating sphere, and the untreated side of the back black treated sample was firmly attached toward the unit, and the reflection spectrum was continuously measured in the wavelength range from 295 nm to 2605 nm. In the measurement, the scan speed was set to 600 nm/min, and the sampling pitch was set to 1 nm. Based on the obtained spectral reflection spectrum, the widest reflection band in which the reflectance is continuously 20% or more over 100 nm or more was taken as Π, the reflection bandwidth of this wavelength band Π was taken as λ, and the average reflectance of the reflection band was taken as R. In addition, the maximum reflectance and average reflectance in the wavelength range of 400 to 800 nm, and the average reflectance in the wavelength range of 900 to 1200 nm were also similarly taken from the obtained reflection spectrum. The average reflectance was also measured in the same manner for the stretched samples (1.3 times × 1.3 times stretched sample and 1.5 times × 1.5 times stretched sample) prepared according to the method described in (9), and the average reflectance changes ΔR1 and ΔR2 were calculated by the following formula.
ΔR1=(average reflectance R before stretching−average reflectance R of sample stretched 1.3 times)/average reflectance R before stretching×100(%)
ΔR2=(average reflectance R before stretching−average reflectance R of sample stretched 1.5 times)/average reflectance R before stretching×100(%).

(5) Cross-cut peeling rate The cross-cut peeling rate was evaluated according to the adhesion (cross-cut) test method specified in JIS K 5600-5-6 (1999). Using a 1 mm interval cross-cut guide CCJ-1 manufactured by COTEC, 11 orthogonal cuts were made vertically and horizontally at an angle of 20 to 30° with an NT cutter to create 100 squares. A 24 mm wide "Cellotape" (registered trademark) manufactured by Nichiban Co., Ltd. was attached to the squares, and the tape was quickly peeled off at an angle of about 60°, and the number of squares that were completely peeled off was read. This operation was repeated 10 times, and the average number of peeled squares was calculated to calculate the peeling rate.

(6) Saturation The chromaticity (a ^* , b ^* ) of a film having a product width of 1 m was measured at each point at intervals of 10 cm in the width direction using a spectrophotometer CM-3600d manufactured by Konica Minolta Sensing Co., Ltd. The chromaticity was calculated from the obtained chromaticity, and the difference between the maximum and minimum chroma values was defined as the chroma range.
The measurement procedure was as follows: zero calibration of the reflectance was performed using the zero calibration box attached to the spectrophotometer, followed by 100% calibration using the attached white calibration plate, and then the chromaticity (a ^* , b ^* ) of the film was measured under the following conditions.
Mode: Reflection, SCI/SCE simultaneous measurement Measurement diameter: 8 mm
Sample: Black ink was applied to the non-measurement side, and the chroma C* was calculated from the chromaticity (a ^* , b ^* ). The definition of chroma is as follows: The closer the chroma is to 0, the less colored the sample is.
C* = ((a ^* ) ^² + (b ^* ) ^² ) ^½
The chromaticity (a ^* , b ^* ) used in calculating saturation was the SCI value.
The saturation was also measured for a sample stretched to 1.3 times its area magnification produced by the method described in (9), and the saturation change ΔC* was calculated as follows.
ΔC*=(chroma C* of 1.3-fold stretched sample−chroma C* before stretching)/chroma C* before stretching×100(%).

(7) Haze A haze meter (HGM-2DP) manufactured by Suga Test Instruments Co., Ltd. was used. A sample was cut out from the center of the film width direction to a size of 10 cm x 10 cm, and the total light transmittance and haze value were measured according to the old JIS-K-7105 (1994). Measurements were taken at three points at equal intervals in the film width direction, and the average value was used as the measurement result.

(8) Long-term reliability test A thermohygrostat (LHL-114) manufactured by Espec Corp. was used. A sample of 10 cm square was cut out from the obtained laminated film, and the sample was placed between two sheets of plain paper and left to stand in the thermohygrostat. After standing for 500 hours, the cross-cut peel rate described in (5) and the haze value change (Δ haze) described in (7) were evaluated and rated as A to D as follows.
A: The change in peel rate was 1% or less, and the Δ haze was 0.1% or less.
B: Not corresponding to A, the change in peel rate was 5% or less, and the Δ haze was 0.5% or less.
C: Not corresponding to either A or B, the change in peel rate was 10% or less, and the Δ haze was 1.0% or less.
D: None of A to C applied.

The thermoplastic resin, additives, and water-based coating material X used in the examples of the present invention are described below. The amount of copolymerization components in the polyester resin described here represents the amount of copolymerization relative to 100 mol% of the acid component and 100% of the diol component.

(9) Preparation of stretched samples Bruckner film stretcher KARO-V was used to prepare the stretched samples. The obtained laminated film was cut into 100 mm squares and simultaneously biaxially stretched at a temperature of 100° C. to a stretch ratio of 1.3 times (main orientation axis direction) × 1.3 times (main orientation axis perpendicular direction) or 1.5 times (main orientation axis direction) × 1.5 times (main orientation axis perpendicular direction). The stretching speed was 200%/min. In the production of the laminated films of the examples and comparative examples, the films were stretched in the longitudinal direction and the width direction, so that it is clear that the main orientation axis direction and the direction perpendicular to the main orientation axis of the film were either of these. That is, in the preparation of the stretched sample, the laminated film was stretched in the longitudinal direction and the width direction.

<Thermoplastic resin>
In each example, the following resins 1 to 11 were used as shown in Tables 1 to 3. Of the following resins 1 to 11, resins 1, 2, 4, 7, 9, and 11 are crystalline, resin 3 is semi-crystalline, and resins 5, 6, 8, and 10 are amorphous.
Resin 1: Crystalline homopolyethylene terephthalate resin exhibiting a glass transition temperature of 78°C, a melting point of 254°C, and a melting enthalpy of 40 J/g. Resin 2: Crystalline polyethylene terephthalate resin copolymerized with 10 mol% isophthalic acid exhibiting a glass transition temperature of 79°C, a melting point of 230°C, and a melting enthalpy of 12 J/g. Resin 3: Semicrystalline polyethylene terephthalate resin copolymerized with 15 mol% isophthalic acid exhibiting a glass transition temperature of 77°C, a melting point of 217°C, and a melting enthalpy of 2 J/g. Resin 4: Crystalline polyethylene naphthalate resin copolymerized with 5 mol% polyethylene glycol having a molecular weight of 400 exhibiting a glass transition temperature of 97°C, a melting point of 254°C, and a melting enthalpy of 33 J/g. Resin 5: Amorphous polyethylene terephthalate resin copolymerized with 33 mol% cyclohexane dimethanol exhibiting a glass transition temperature of 80°C. Amorphous polyethylene terephthalate resin 7 copolymerized with 20 mol% spiroglycol, exhibiting a glass transition temperature of 77 ° C.: Crystalline acid-modified ethylene-propylene copolymer resin 8, exhibiting a melting point of 133 ° C. and a melting enthalpy of 2 J / g: Amorphous homo-polymethyl methacrylate resin 9, exhibiting a glass transition temperature of 101 ° C.: Crystalline polymetaxylenediamine adipamide resin 10, exhibiting a glass transition temperature of 86 ° C., a melting point of 237 ° C., and a melting enthalpy of 10 J / g: Amorphous thermoplastic resin 11, exhibiting a glass transition temperature of 99 ° C., kneaded with resin 4 and resin 8 in a volume concentration ratio of 50:50: A crystalline polyethylene terephthalate resin copolymerized with 8 mol% 5-sodium sulfoisophthalic acid dimethyl, exhibiting a glass transition temperature of 78 ° C., a melting point of 253 ° C., and a melting enthalpy of 22 J / g.

<Additives>
An acrylic polymer having an epoxy value of 1.4 meq/g and an average molecular weight of 2900 g/mol.

<Water-based coating agent X>
A material obtained by mixing the following polyester resin 1 (100 parts by mass), reactive compound 1 (30 parts by mass), and reactive compound 2 (30 parts by mass) was mixed with 0.5 parts by mass of colloidal silica particles having a particle size of 100 nm per 100 parts by mass of binder resin, which corresponds to the mixture of the resins and compounds, and the solids concentration was adjusted to 5 parts by mass with water as a solvent. After that, 0.03 parts by mass of a surfactant was added per 100 parts by mass of water in total, and mixed to obtain a coating composition.
Polyester resin 1:
An aqueous dispersion of polyester resin having the following copolymerization composition was obtained by the following procedure. The following copolymerization components and 0.1 parts of potassium titanium oxalate as a catalyst were added to a reactor, and the temperature was raised to 200°C while stirring and mixing in a nitrogen atmosphere at normal pressure. Next, the reaction temperature was gradually raised to 250°C over 4 hours to terminate the transesterification reaction. 15 parts by mass of this polyester resin and 85 parts by mass of water were added to a dissolution tank and dispersed at a temperature of 80 to 95°C over 2 hours with stirring to obtain a 15% aqueous dispersion of polyester resin.
(Copolymer Composition)
Dicarboxylic acid component: dimethyl 2,6-naphthalenedicarboxylate: 88 mol%
Sodium dimethyl 5-sulfoisophthalate: 12 mol%
Diol component: Compound in which 2 moles of ethylene oxide are added to 1 mole of bisphenol A: 86 mole%
1,3-propanediol: 14 mol%
Reactive Compound 1:
Carbodiimide water-based crosslinking agent (Nisshinbo Chemical Co., Ltd. "Carbodilite" (registered trademark) V-04)
Reactive Compound 2:
Oxazoline-containing polymer aqueous dispersion ("Epocross" (registered trademark) WS-500, manufactured by Nippon Shokubai Co., Ltd.).

Example 1
Resin 1, resin 2, and resin 5 were used in order as the thermoplastic resins constituting the thermoplastic resin layers A, B, and C, respectively. Each of the prepared thermoplastic resins was separately charged in pellet form into three twin-screw extruders, and resin 1, resin 2, and resin 5 were melted and kneaded at 270 ° C, 270 ° C, and 280 ° C, respectively. The kneading conditions were set so that the screw rotation speed relative to the discharge amount was 0.7 in all cases. Next, after passing through seven FSS-type leaf disk filters, the mixture was merged in a feed block with 601 slits adjusted to 270 ° C while being metered with a gear pump, and a 601-layer laminate was formed in which the lamination ratio was 0.98 for A layer/B layer and 1.02 for C layer/B layer, and the layers were laminated in a regular arrangement of A layer/B layer/C layer/B layer in the thickness direction, and both surface layers were A layers. Here, the slit length and width in the feed block were designed so that the layer thickness increases monotonically from the outermost surface on one side to the outermost surface on the other side, except for both outermost layers, and the gradient of layers A to C (the ratio of the maximum layer thickness to the minimum layer thickness (maximum layer thickness/minimum layer thickness) of the part showing a monotonous increase in the layer thickness distribution) was 2.0. Thereafter, the laminate that passed through the feed block was supplied to a T-die and molded into a sheet, and then, while applying an electrostatic voltage of 8 kV with a wire, it was rapidly cooled and solidified on a casting drum whose surface temperature was kept at 25 ° C. to obtain an unstretched laminated cast sheet. The obtained laminated cast sheet was heated with a roll group set at 70 to 80 ° C., and then stretched 3.3 times in the longitudinal direction at a temperature of 85 ° C. while being rapidly heated by a radiation heater from both sides of the cast sheet within a stretching section length of 100 mm, and then cooled once. Subsequently, both sides of the obtained uniaxially stretched film were subjected to corona discharge treatment in air to set the wet tension of the base film to 55 mN/m, and then both sides were coated with water-based coating agent X for forming a slippery layer using #4 metabar (hereinafter, coating means the above content), forming a slippery layer. Furthermore, this uniaxially stretched film was introduced into a tenter, preheated with hot air at 85°C, and then stretched 3.6 times in the film width direction at a temperature of 90°C. The biaxially stretched film was heat-set with hot air at 200°C immediately after transverse stretching, and was subjected to 5% relaxation treatment in the width direction just before the tenter exit, and then wound up. The evaluation results of the obtained laminated film are shown in Table 1.

(Examples 2 to 10, 13, 14, 16, 17, 19 to 21, Comparative Examples 2 and 4)
A laminate film was obtained in the same manner as in Example 1, except that the resin of each layer, the film configuration, and the film-forming conditions were changed as shown in Tables 1, 2, and 3. The evaluation results of the obtained laminate film are shown in Tables 1, 2, and 3. The film thickness was adjusted by adjusting the take-up speed of the cast drum, and the lamination ratio was adjusted by adjusting the discharge rate of the extruder (the same applies to the other examples and comparative examples below).

(Examples 11 and 12)
A laminate film was obtained in the same manner as in Example 10, except that a predetermined concentration of an epoxy end modifier for improving adhesion was pre-compounded into the thermoplastic resin shown in Table 2 and used as the thermoplastic resin constituting the thermoplastic resin layer. The evaluation results of the obtained laminate film are shown in Table 2.

(Example 15)
In Example 14, resin 2, resin 5, and resin 6 were used in order as the thermoplastic resins constituting the thermoplastic resin layers A, B, and C, respectively. Furthermore, as a lamination device, two slit plates having 301 slits were used, and the slit length and width in the feed block were designed so that the layer thickness increases monotonically from the outermost surface on one side to the intermediate layer (301 layer) except for both outermost layers and the intermediate layer (301st layer), and the layer thickness decreases monotonically from the intermediate layer to the outermost layer on the opposite side. A laminated film was obtained in the same manner as in the manufacturing method described in Example 14, except that the film formation conditions were changed as shown in Table 2, using a feed block with 601 slits. It was confirmed by observation with a transmission electron microscope that both surface layers and the intermediate layer showed a thick film layer of 5 μm. The evaluation results of the obtained laminated film are shown in Table 2.

(Example 18)
In Example 1, resin 1, resin 5, and resin 6 were used in order as the thermoplastic resins constituting the thermoplastic resin layers A, B, and C, respectively. Furthermore, as a lamination device, a feed block having three slit plates with a total of 799 slits was used, which was designed to show a layer thickness distribution in which the layers are laminated in a regular arrangement of A layer/B layer/C layer in the thickness direction and the layer thickness increases monotonically from the outermost layer on one side to the outermost layer on the other side, to obtain a molten laminate in which the regular arrangement is A layer/B layer/C layer and the outermost layer on both sides is A layer. In addition, a laminate film was obtained in the same manner as in Example 1, except that the resin of each layer, the film configuration, and the film-forming conditions were changed as shown in Table 2. The evaluation results of the obtained laminate film are shown in Table 2.

(Comparative Example 1)
In Example 2, resin 1, resin 2, and resin 5 were used in order as the thermoplastic resins constituting the thermoplastic resin layers A, B, and C, respectively. Furthermore, as a lamination device, a feed block having three slit plates with a total of 151 slits was used, which was designed to laminate the layers in a regular arrangement of A layer/B layer/C layer in the thickness direction and to show a layer thickness distribution in which the layer thickness increases monotonically from the outermost layer on one side to the outermost layer on the other side, to obtain a molten laminate in which the regular arrangement was A layer/B layer/C layer and the outermost layers on both sides were A layer. The rest was the same as in Example 2 to obtain a laminate film. The evaluation results of the obtained laminate film are shown in Table 3.

(Comparative Example 3)
Resin 4 and resin 8 were used in order as the thermoplastic resins constituting the thermoplastic resin layers A and B, respectively. In addition, the layers were joined in a feed block with 301 slits adjusted to 270°C to form a 301-layer laminate in which the lamination ratio A layer/B layer was 0.86, the layers were laminated in an alternating regular arrangement in the thickness direction, and both surface layers were A layers. Here, the slit length and width in the feed block were designed so that the layer thickness monotonically increased from the outermost surface on one side to the outermost surface on the opposite side, except for both outermost layers. A laminate film was obtained in the same manner as in Example 1, except that the other film-forming conditions were changed as shown in Table 3. The evaluation results of the obtained laminate film are shown in Table 3.

The laminated film of the present invention has a regular arrangement of three different thermoplastic resin layers, and the effect of the third thermoplastic resin layer acting as a buffer layer allows for lamination of thermoplastic resin layers with completely different skeletal structures that increase the difference in refractive index. In addition, the use of three or more thermoplastic resin layers with different optical properties allows for optical designs that could not be achieved with conventional laminated films, and allows for the realization of laminated films with a wide reflection band and high reflectance compared to conventional laminated films, with a low number of layers and thin films. Such laminated films are less likely to break or lose color due to molding, and can be suitably used for molding under conditions of high temperature load, so they can be used without compromising their original optical properties (metallic tone) even in applications where high temperature load is applied, such as decorative molding films for automobiles and home appliances.

1: Reflection spectrum 2: Reflection band Π
3: Wavelength bandwidth λ of reflection band Π
4: Average reflectance of reflection band Π

Claims (13)

The thermoplastic resin layer has three or more different types.
The thermoplastic resin layer has three or more consecutive ordered arrays formed of the three or more types of thermoplastic resin layers,
The average reflectance at wavelengths of 400 nm to 800 nm is 35% or more and 100% or less,
The laminate film is characterized in that when stretched by 30% at 100° C. in the main orientation axis direction and in the direction perpendicular to the main orientation axis, the average reflectance change ΔR1 at wavelengths of 400 nm to 800 nm is 0.1% or more and 20% or less. The thermoplastic resin layer has three or more different types.
The thermoplastic resin layer has three or more consecutive ordered arrays formed of the three or more types of thermoplastic resin layers,
Chroma C* is 0.1 or more and 20 or less,
The laminated film is characterized in that when stretched 30% in the main orientation axis direction and in the direction perpendicular to the main orientation axis at 100° C., the change in saturation ΔC* is 0.1% or more and 15% or less. The laminated film according to claim 1 or 2, characterized in that the peeling rate of the squares is 10% or less in an adhesion test based on the cross-cut method specified in JIS K 5600-5-6:1999. The laminated film according to claim 1 or 2, characterized in that at least one of the three or more different thermoplastic resin layers is a thermoplastic resin layer that exhibits crystallinity. The laminated film according to claim 4, characterized in that at least one of the crystalline thermoplastic resin layers is composed mainly of polyethylene terephthalate or polyethylene naphthalate. The laminated film according to claim 1 or 2, characterized in that the thermoplastic resin layers constituting the regular arrangement are of three types. The laminated film according to claim 6, characterized in that the three types of thermoplastic resin layers constituting the regular arrangement are a combination of crystalline/amorphous/amorphous thermoplastic resin layers. The laminated film according to claim 7, characterized in that at least one of the amorphous thermoplastic resin layers is mainly composed of acrylic, polyester having an alicyclic structure, polyolefin, or polyamide. The average reflectance at wavelengths of 400 nm to 800 nm is 35% or more and 100% or less,
The laminate film according to claim 1 or 2, characterized in that when stretched by 50% at 100 ° C. in the main orientation axis direction and in the direction perpendicular to the main orientation axis, the average reflectance change ΔR2 at a wavelength of 400 nm to 800 nm is 0.1% or more and 20% or less. The laminate film according to claim 1 or 2, characterized in that, in the wavelength range of 300 to 2600 nm, the reflection bandwidth of the widest reflection band Π in which the reflectance is continuously 20% or more over 100 nm or more is λ [nm], the average reflectance in the reflection band R [%], and the film thickness t [μm], shows (λ·R)/t of 820 or more and 1400 or less. The laminated film according to claim 1, characterized in that the chroma C* is 0.1 to 20, and the chroma change ΔC* when stretched 30% in the main orientation axis direction and in the direction perpendicular to the main orientation axis at 100°C is 0.1% to 15%. A decorative film made using the laminated film according to claim 1 or 2. A molded article comprising the decorative film according to claim 12.

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